Variations in tension during winding of a package of a multi-strand material or bundle, such as fiber glass roving, are a significant problem. Fluctuations in tension during winding can cause variations in package density, implosion or telescoping of packages, non-uniform package ends and tangling of the roving during payout. Tension variations and geometry effects during winding are believed to contribute to catenary or sag of multi-strand material. Typical fiber glass rovings can sag about 15 to about 25 centimeters (cm) (about 6 to about 10 inches) over a 15 meter (50 foot) length. This sag can interfere with machinery and/or other nearby rovings and cause undesirable process interruptions.
Various attempts have been made to control bundle tension during winding. For example, U.S. Pat. No. 3,966,133 discloses a tension controlling apparatus in which roving wraps alternately under and over a series of parallel tensioning bars. During the winding process, the yieldable biasing force of the upper tensioning bars can be adjusted to regulate the roving tension in response to increased roving package diameter.
U.S. Pat. No. 3,765,988 discloses an apparatus for packaging linear material. Tension control means are located adjacent each supply package for maintaining equal tension between each strand withdrawn from each package. The strands are wrapped about a major portion of the circumference of a motor-driven feed roll having manually adjustable guide rolls for regulating the length of strand contacting the feed roll. When the strand loses tension, the biased pivotable arm of the winder engages a limit switch which de-energizes the winder motor.
U.S. Pat. No. 3,792,821 discloses a method and apparatus for packaging a composite roving. The tension of each roving can be adjusted. The rovings are fed through rotatable pulleys and guide means to a pull roll driven by a motor at a substantially constant speed. The rovings wrap around a major portion of the circumference of the pull roll, about a cooperating nip roll, and to a guide member carried upon a pivotally supported tension control arm of a winder. Breakage of any of the rovings causes the corresponding pulley to cease rotation and signals the apparatus to stop the winding process.
U.S. Pat. No. 3,808,789 discloses a system for twisting yarns. Individual strands from supply packages are passed through a feed mechanism consisting of three parallel drive rollers and two idler rollers staggered between and biased downwardly into contact with the drive rollers, causing the strands to wrap around a portion of the circumference of each roller. Variations in the strand tension are then sensed and compensated for by adjustment of the feed roller speed. The strands are fed to a strand separator, through a balloon zone, conventional tension compensating system and a winder.
The LEESONA "Catenary-free" tow winder Models 995/966, 967 and 968, commercially available from Leesona Division of John Brown Textile Machinery of Burlington, N.C., pass strands through multiple godets to stabilize the strands by tensioning straightness and about a tension arm for tensioning the roving prior to winding. These winders, however, produced unacceptable levels of fuzz when used to process conventional glass fiber bundles.